The present invention relates generally to a membrane enzyme reactor, and more particularly to a membrane enzyme reactor containing a plurality of biocatalyst-immobilized sheets to facilitate the continuous operation of the reactor, so as to produce foods, drugs, and the like.
The conventional bioconversion of the raw materials into foods, pharmaceutical products, and other bioproducts involves the use of the granular biocatalyst which is fed into a reactor to form a fixed bed or a fluidized bed.
The use of the granular immobilized biocatalyst often results in the slow reaction rate and the large Michaelis constant (Km). In addition, the porous granules are susceptible to pore blockage. Further, the uneven channeling often takes place in the operation of the fixed bed reactor. For this reason, the membrane enzyme reactor was developed, in which the soluble enzyme or other biocatalysts are confined to a specific space by means of the ultrafiltration membrane, or are immobilized onto the ultrafiltration membrane. The bioconversion is then brought about by causing the confined or immobilized enzymes or biocatalysts to make contact with a reactant mixture, thereby resulting in the production of an end product which is then forced to penetrate the ultrafiltration membranes under pressure. The ultrafiltration membrane may take the form of a flate sheet, a hollow fiber, a spiral wound, a tube, or a stirred cell. For more details on the membrane enzyme reactors, please refer to a literature published by Prazeres and Cabral in ENZYME MICROB. TECHNOL., 16, 738-750, 1994. These conventional membrane enzyme reactors are generally defective in design in that their production rate slows down rapidly during operation because of the loss of the catalytic and mass transfer efficiencies.
Certain conventional membrane enzyme reactors contain enzymes which are immobilized in the interior of the membrane, such as the internal pores of a ceramic microfilter. The conversion reactions are catalyzed by the enzyme by passing the reactant mixture through the internal pores of the microfilter, so that the filtering function is sacrificed. For more details, please refer to a literature published by Harrington et al., in ENZYME MICROB. TECHNOL., 14, 813-818, 1992. The ceramic microfilter is not cost-effective and is defective in design in that it is difficult to remove the deactivated enzymes from the internal pores of the ceramic microfilter.
The primary objective of the present invention is to provide a membrane enzyme reactor which is free of the drawbacks of the conventional membrane enzyme reactors described above.
The membrane enzyme reactor of the present invention comprises a container, a cap, and a plurality of supporting frames.
The container has a bottom, four upright walls circumventing the bottom, and a top opening which is defined by the four upright walls. Two opposite side walls of the four upright walls are provided correspondingly with plural pairs of grooves. The four upright walls are provided on a front wall thereof with an inlet.
The cap has a plurality of holes, which are arranged at an interval. The top opening of the container is sealed off by the cap.
Each of the supporting frames has a frame, and a supporting mesh is circumferentially fixed with the frame for depositing thereon a immobilized biocatalyst. The supporting frames are received by said plural pairs of grooves of the container, so that the container is divided by the supporting frames into a plurality of cells. The number of the supporting frames is one less than the number of the cells.
One of the holes of the cap is kept open for use as an outlet while the remaining holes of the cap are sealed off. A rear wall of the upright walls may be provided with an outlet in place of the outlet of the cap, whereas the holes of the cap are all sealed off. A liquid is guided into the container via the inlet such that the liquid flows through the supporting mesh before being let out of the container via the outlet.
In addition to the membrane enzyme reactor, the present invention also discloses a method for producing the bioproducts by using the immobilized biocatalyst in conjunction with the membrane enzyme reactor.
The method of the present invention includes a first step in which an immobilized biocatalyst is deposited on the supporting meshes of the supporting frames of the membrane enzyme reactor. The immobilized biocatalyst comprises a porous matrix and a biocatalyst entrapped therein. A liquid reaction mixture is then guided into the container via the inlet. Thereafter, the product mixture is collected via the outlet of the container.
Preferably, the membrane enzyme reactor of the present invention further comprises a partition plate, which is located by a pair of said plural pairs of grooves of the container such that the supporting frames are located between the partition plate and the front wall of the container. The liquid is guided into the container via the inlet such that the liquid flows through the supporting meshes, and that the liquid is then let out via the outlet of the cap.
Preferably, any two adjoining cells in the container are in communication with each other only via the supporting mesh of the supporting frame which separates the two adjoining cells, when the supporting frames of the membrane enzyme reactor of the present invention are received in said plural pairs of grooves of the container.
Preferably, any two adjoining cells in the container are in communication with each other via the supporting mesh of the supporting frame which separates the two adjoining cells and via an opening provided on the frame of the supporting frame, when the supporting frames of the membrane enzyme reactor of the present invention are received in said plural pairs of grooves of the container.
Preferably, the cap of the membrane enzyme reactor of the present invention is joined with the top opening of the container by threading fixation means in conjunction with a rubber gasket which is disposed between the cap and the top of the container.
Preferably, the method of the present invention involves recycling a portion of the product mixture flowing out of the container to the container via the inlet.
The supporting frames of the present invention are provided with the immobilized biocatalyst attached thereto and are also called biocatalyst-immobilized sheets throughout this specification. The sheets can be easily prepared and replaced. In addition, the sheets have a low trans-membrane pressure and a low intra-membrane diffusion resistance in relation to the liquid reaction mixture. The membrane enzyme reactor of the present invention is therefore suitable for use in producing continuously a variety of the value-added bioproducts. In light of the reactor of the present invention being adapted to accommodate a plurality of the sheets, the reactor is thus provided per unit volume thereof with a greater amount of biocatalyst so as to enhance the productivity of the reactor.